A track type tractor includes a modular track roller frame made up of easily assembled sub-components. Known door locks having a closing aid have an increased space requirement and cannot readily be accommodated in structurally predetermined constructional spaces. The identification code further includes a letter designation of the type of animal and the individual animal’s number within the owner’s herdflock, as well as a two letter designation of the animal’s country of origin. The barrier image layer can include opaque barriers or can include translucent or transparent barriers. The recess separates the tile into at least two parts which are totally separated one from another, which parts exhibit upper edges which are located side-by-side and which are destined to be brought into reciprocal contact in order to give the tile a predetermined non-flat conformation. Each of the terminals has a noise filter function, and is fixed to the shield case.